A response surface analysis of the aqueous leaching of amylose from maize starch

Abstract A response surface analysis with a face centered central composite design was implemented to study the effect of maize ( Zea mays L.) starch concentration (3.0–7.0% w/v) and leaching temperature (LT, 70–90 °C) on aqueous leaching of amylose (AM) as a way to optimize the conditions for obtaining the highest yield of long chain AM [number average degree of polymerization (DP n ) ranging between 860 and 930] and highest purity. Second order empirical models were fitted via the least squares approach. Negligible terms were removed using backwards model reduction. Negligible lack of fit terms were obtained for the responses total leached carbohydrate and DP n . The optimization was complemented with a desirability test using the purity of the extracts. As targets for the optimization, maximum leachate yields, DP n  ≈ 900, and purity >95% were set. The reported contour plots and prediction profilers can be used for tailor made production of leachates. Temperature had the most significant main effect as yields and DP n increased with temperature at the expense of purity. Purity was highly compromised when treatments were above 85 °C. This was reflected in the high DP n values (>1500) which suggested the presence of amylopectin material. When using 3.0% (w/v) maize starch suspension at an LT of 81 °C, the largest yield (15.0% of starch) of high DP n AM chains (DP n  ∼ 900) and less than 3.3% of non-AM material were obtained.